(1) Field of the Invention
The present invention relates to a rocker arm spring for use in a valve actuating mechanism of an internal combustion engine and, more particularly, to a rocker arm spring for a valve actuating mechanism of the type which comprises an overhead cam shaft and wherein a rocker arm is swingably supported on the cylinder head of the engine through a universal pivot.
(2) Description of the Related Art
A valve actuating mechanism for an internal combustion engine is known which comprises a rocker arm swingably supported at one end on the cylinder head by means of a universal pivot and wherein an overhead cam shaft engages the mid portion of the rocker arm to operate an intake or exhaust valve of the engine (see, for example, British Patent Specification No. 875,350, published Aug. 16, 1961; U.S. Pat. No. 3,563,215, granted to Ross on Feb. 16, 1971; and British Patent Specification No. 1,437,567, published May 26, 1976). The universal pivot comprises a part-spherical socket formed in the one end of the rocker arm, the socket receiving a part-spherical head of a fulcrum stud. A spring clip assembly in the form of a hairpin spring is used to hold the socket in contact with the stud head.
British Patent Specification No. 963,995, published July 15, 1964, discloses another type of valve gear arrangement in which an end of the rocker arm is also supported by a universal pivot. The universal pivot comprises a support socket mounted on the cylinder head and having a part-spherical concave bearing surface, and a pivotable shaft adjustably mounted to the rocker arm and having a part-spherical convex lower end engaging with and resting on the bearing surface of the support socket. As shown in FIG. 3 thereof, the valve gear arrangement includes a rocker arm spring in the form of a leaf spring having a loop configuration, the upper arm of which has an end clamped to the rocker arm. The lower arm of the leaf spring is clamped to the support socket. The leaf spring serves to take up any play in the universal pivot and to hold the rocker arm in contact with the valve stem.
In a copending U.S. patent application Ser. No. 460,021, filed Jan. 21, 1984 and assigned to the assignee of the present invention, there is disclosed a valve actuating mechanism also having a rocker arm spring of the leaf spring type. This rocker arm spring is roughly U-shaped and has an upper arm section engaging the rocker arm. The lower arm section has a forked end which is fitted within a circumferential groove formed in a support socket secured to the cylinder head. In this arrangement, the thickness of the rocker arm spring is smaller than the width of the circumferential groove so that the forked end of the lower arm section is loosely fitted in the groove and that the forked end is urged for support against the upper side wall of the groove by the spring force. The play present between the side walls of the groove and the forked end of the lower arm permits the forked end to rattle within the groove as the rocker arm spring vibrates in response to the swinging movement of the rocker arm. This causes premature failure and undue wear of the rocker arm spring.